Biomass and organic wastes are renewable energy sources. Both these sources have the potential to be utilized for the production of Green Energy. Pyrolysis and gasification processes have been known for the decomposition of biomass and organic materials and their utilization in generating energy which could be used for number of purposes. Even though pyrolysis or gasification have been reported to be used for the utilization of biomass and organic materials, still their application on a commercial scale has been on a limited level, reason being reduced process energy efficiency, low calorific value, high gas volume, very high tar content in the gas, high temperature zones, the design of the system is such that it has been limited to handle single feedstock, thereby limiting the use of the system.
U.S. Pat. No. 7,077,878 disclose a process for gasifying organic materials. The system used to carry out the process comprises of, the heating up zone, the second reaction zone (reformer) and a pyrolysis reactor. These are successively connected one after the other from the top down. The process comprises the steps of introducing the organic material into a pyrolysis reactor. The organic materials come in contact with the heat carrying medium dropping from the heating up zone in the pyrolysis reactor and are split into a carbon containing residue and pyrolysis gases. The pyrolysis gases are moved to the second reaction zone. The carbon containing residue and the heat carrying medium proceed to a separation stage, whereby the carbon containing residue and the heat carrying medium are separated. The heat carrying medium is passed to the heating up zone and the carbon containing residue is further burned in a firing stage. The burning of the carbon containing residue generates hot exhaust gases which is passed to the heating up zone to pass their heat to the heat carrying medium. The heat carrying medium is further extracted into the second reaction zone wherein it heats the already present mixture of pyrolysis gases and the reactant steam converting it to the product gas. The mixture of pyrolysis gas and reactant steam also receives heat from the firing stage. The heat carrying medium is further recycled to the pyrolysis reactor. As can be seen, this process utilizes the heat carrying medium in every stage. Also, the heat is transferred from the firing stage to the heating up zone and the second reaction zone. This process requires lot of heat transfer resulting in a wastage of significant amount of energy. Also, the heat carrying medium is of uniform size.
CA 02496907 discloses a process to recover hydrogen from organic wastes. The process comprises of heating organic wastes under a non-oxidative atmosphere at a temperature from 500 to 600 deg C. The pyrolysis gases obtained are mixed with steam at a temperature from 900-1000 deg C. to obtain reformed gases from which hydrogen is separated. The heat to carry out the pyrolysis and reforming reactions are provided by heat carrying mediums. In this process, heat carrying medium is used in both, the pyrolysis as well as the reforming stage. This process utilizes the heat carrying medium in every stage. This process requires lot of heat transfer resulting in wastage of significant amount of energy.
U.S. Pat. No. 6,084,147 disclose a two stage method for decomposing waste materials. Both the stages are carried out in steam reformers connected back to back containing inert media bed made of large, high density beads such as alumina beads. The fluidizing gases composed of oxygen and superheated steam are injected in the first stage, wherein they pyrolyze the wastes at a temperature in the range of 450 deg C. to 800 deg C. Carbon and unpyrolysed wastes are carried to the second stage, wherein pyrolysis continues under essentially under the same conditions as that of the first stage. The gases generated in the process are treated in conventional ways. This invention also involves Fluidized bed with the fluidizing gases, being a mixture of air/oxygen/nitrogen, adding to the overall gas volume and thus diluting the final gas calorific value and limiting economical utilization.
U.S. Pat. No. 6,048,139 discloses a method for processing waste or biomass material comprising the steps of a) the waste or biomass material is subjected to a pyrolysis at a temperature of 350-650. degree. C advantageously 450-550. degree. C.; (b) the gas released in the course of the pyrolysis is subjected without condensation to a cracking treatment at a temperature of 1100-1600. deg C., advantageously 1200-1400. deg C., under the influence of oxygen-rich gas introduced from outside and possibly of steam; (c) the residue liberated in the course of the pyrolysis is gasified under a pressure of 0.5-1.5 bar, advantageously 0.8-1.2 bar, at a temperature of 1200-1700. deg C., advantageously 1400-1600. deg C., and is volatilized or, as the case may be, fused under reducing conditions; (d) the fused slag or metal concentrate obtained under stage (c) is discharged or, as the case may be, recovered; (e) the product gases obtained in the course of stages (b) and (c) are combined or not combined and then subjected to gas cleaning.